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january 3rd potential coastal grazer


forkyfork
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11 minutes ago, MJO812 said:

Going with the Nam? Possible but this will come down to 0z tonight. 

If you go with the NAM we get nothing at all. Not even a coating to an inch. But maybe something like what 12z RGEM is showing will happen, with our area on the northern fringe and getting brushed by a coating to an inch. Hard to be optimistic about more than that right now. When you have only 1 major model on your side, you certainly don't want it to be GFS. But stranger things have happened, so we still have a slight chance.

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Soooooo much variability.  I think a watch will be needed for a portion of NYC subforum...up to and including Monmouth County to eastern LI.  A watch is not a warning but it signifies potency and be alert. NWS can describe the options in the details.  Watches should verify about 50% of the time, probably higher verification in shorter lead time.  

These graphics from the SPC SREF are surprising to me but not so for the GFS.   Wow! Both the 03z and 09z have mean some where near 5" LGA.  This is up from 0.2" 15z cycle yesterday and 2" in the 21z cycle yesterday.   

Big banding signal for for S NJ. NYC best time for a burst of snow seems 10A-1P. 

Screen Shot 2022-01-02 at 11.14.15 AM.png

Screen Shot 2022-01-02 at 11.14.36 AM.png

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26 minutes ago, MJO812 said:

Gefs west 

gfs-ememb_lowlocs_eus_6.png

A lot of the members are tucked, but none really gaining latitude. We need this off DE and for it to move NE and not E or ENE. The GFS does look pretty interesting in the mid- and upper levels though. And I'm glad to see precipitation moving into southern OH - that's been a milepost for me in getting precip. to NYC.

Right now tomorrow is shaping up to be a painful day of radar watching and wishing.

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4 minutes ago, eduggs said:

A lot of the members are tucked, but none really gaining latitude. We need this off DE and for it to move NE and not E or ENE. The GFS does look pretty interesting in the mid- and upper levels though. And I'm glad to see precipitation moving into southern OH - that's been a milepost for me in getting precip. to NYC.

Right now tomorrow is shaping up to be a painful day of radar watching and wishing.

Agree

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25 minutes ago, Rjay said:

I think the href has the right idea although I can see the 1" line getting into EWR and NYC.

I sort of do too...  and NAM idea of dry layers near 850 MB looks good NYC, but this system is showing better 500MB separation and tending to go negative as it whips out to the se of Cape Cod.  I do not like the SREF being so abundant this far north (especially SPC SREF plumes).  It won't take much for big snow growth and I expect we will see 1-2"/hr snowfall rates for a couple of hours mid late morning somewhere very close to Toms River... may still be south of there but I think now is not the time to hold onto a snowfree forecast.  Folks need to be aware of potential and if it misses south of NYC... excellent.  I just don't think our modeling is that good to be so determinant that nothing will happen, in the face of the ensembles, GFS/ SPC SREF plumes etc. 

Mt Holly made the right move, 6 hours late but enough to prep their folks. Going to be quite a storm for 6-12 hours Baltimore area to ACY and probably a bit further nw. 

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19 minutes ago, wdrag said:

Soooooo much variability.  I think a watch will be needed for a portion of NYC subforum...up to and including Monmouth County to eastern LI.  A watch is not a warning but it signifies potency and be alert. NWS can describe the options in the details.  Watches should verify about 50% of the time, probably higher verification in shorter lead time.  

These graphics from the SPC SREF are surprising to me but not so for the GFS.   Wow! Both the 03z and 09z have mean some where near 5" LGA.  This is up from 0.2" 15z cycle yesterday and 2" in the 21z cycle yesterday.   

Big banding signal for for S NJ. NYC best time for a burst of snow seems 10A-1P. 

Screen Shot 2022-01-02 at 11.14.15 AM.png

Screen Shot 2022-01-02 at 11.14.36 AM.png

Those plumes are amazingly well distributed. Tiny bit of clustering 0-2" and then good spacing from 2 -20". Right now I would go with some light snow, dusting to an inch for NYC. Still tons of dry air near 700mb. But big bust potential on the high end. I like WS watch to Monmouth Co. NJ. But what's the criteria there?

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19 minutes ago, MJO812 said:

Cmc keeps coming northwest. 

 

 

But we're still looking at SNJ, maybe coastal CNJ, and the Islands off MA for any appreciable snow. Maybe now we're also looking at LI possibly back to NYC as well as the SE coast of MA for an inch or two. That's not fundamentally different than where we were at yesterday.

We need to see significant snow getting into northern MD, SEPA before we can start thinking about accumulating snow in and around NYC.

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19 minutes ago, eduggs said:

Those plumes are amazingly well distributed. Tiny bit of clustering 0-2" and then good spacing from 2 -20". Right now I would go with some light snow, dusting to an inch for NYC. Still tons of dry air near 700mb. But big bust potential on the high end. I like WS watch to Monmouth Co. NJ. But what's the criteria there?

Criteria.  My guess still 6 in 12 and 8 in 24.  and/OR  combined PUBLIC IMPACT.  If I was in the drivers seat with more internal info and collaborating across the NWS borders,  I'd argue for a watch = brief high impact potential in the 8A-4P time frame.  It's a watch. Rush hour impact or residuals of and clearly there is big bust potential. Can't be afraid to be wrong.

Preparation is critical for the infrastructure, already impacted by Covid.   They can use the probs to help prep folks. If it misses south, the guidance is there to support the decision making.  

I add the possibly biased high SREF chc of 1"/hr. Use the legend for prob.  I checked blizzard conditions and those are just 20 mi offshore of LI and the NJ coast at 18z Monday.  By the way this graphic data is probably not used in NWS... i still it valuable for me from the old school days which for me still work well, with the exception of not having the improved details of modeled soundings and snow growth. 

 

Graphic added 1209P

 

Screen Shot 2022-01-02 at 12.07.38 PM.png

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If you loop the past 2 days of GFS runs, you see our system at H5 shift steadily south and west and become increasingly deep and negatively tilted. However, modeled heights off New England and the Canadian Maritimes have not really risen. As a result, we've seen the surface reflection really tuck up into western NC and push a lot of moisture further north into the mid-Atlantic. But regardless of this early northward push, the entire system inevitably gets shunted eastward, which prevents the precipitation shield from expanding NW up the coast.

At some point, the main system could gain enough latitude that even with an eastward shunt most of the area is into plowable snow. But that would mean most of CPA is already in the game.

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Also, probably gone unnoticed GFS nothing for the 7th...  GGEM snowstorm I95 nwwd.  

Mondays storm is first up.  If the GFS and SREF fail too high or the NWS ensemble blend and  

NAM are too low.  There modelers will argue sensitivity to the interactions...they are correct. 

 

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5 minutes ago, wdrag said:

Criteria.  My guess still 6 in 12 and 8 in 24.  and/OR  combined PUBLIC IMPACT.  If I was in the drivers seat with more internal info and collaborating across the NWS borders,  I'd argue for a watch = brief high impact potential in the 8A-4P time frame.  It's a watch. Rush hour impact or residuals of and clearly there is big bust potential. Can't be afraid to be wrong.

Preparation is critical for the infrastructure, already impacted by Covid.   They can use the probs to help prep folks. If it misses south, the guidance is there to support the decision making.  

I add the possibly biased high SREF chc of 1"/hr. Use the legend for prob.  I checked blizzard conditions and those are just 20 mi offshore of LI and the NJ coast at 18z Monday.  By the way this graphic data is probably not used in NWS... i still it valuable for me from the old school days which for me still work well, with the exception of not having the improved details of modeled soundings and snow growth. 

 

If you're a person in, say, Asbury Park, NJ, with an average interest in the weather... how are you supposed to interpret:

20% chance of <1"

50% chance >2"

30% chance of 6"+ (in 8 hours)

10% chance of 10"+ 

I guess you go with the Watch. But the public doesn't read forecast discussions. I guess people just check their weather apps nowadays. 

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The 12z guidance would put  ACY in top 10 snowiest January day range.

 

Maximum 1-Day Total Snowfall 
for Atlantic City Area, NJ (ThreadEx)
Click column heading to sort ascending, click again to sort descending.
Rank
Value
Ending Date
Period of record: 1945-01-31 to 2022-01-01
1 14.3 1987-01-26
2 13.2 2018-01-04
3 12.9 1964-01-13
4 12.7 1996-01-07
5 10.1 2016-01-23
6 8.3 2000-01-25
7 8.0 1961-01-19
8 7.7 2011-01-08
9 7.6 2010-01-30
10 7.4 1958-01-07
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Added the criteria for 12 hour WATCH snowfall.  It's verified as an average in the zone-county.  THIS I NOT a NWS snowfall forecast map, only answering some of the base criteria for issuing a WATCH. Pleas make sure this is not mis interpreted as a snowfall forecast map.

Color coded   here you are.

Also a link to the NWS snow probabilities and Winter Storm Severity Index is below, as of 10AM.

https://www.weather.gov/phi/winter

 

 

Screen Shot 2022-01-02 at 12.17.23 PM.png

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10 minutes ago, eduggs said:

If you're a person in, say, Asbury Park, NJ, with an average interest in the weather... how are you supposed to interpret:

20% chance of <1"

50% chance >2"

30% chance of 6"+ (in 8 hours)

10% chance of 10"+ 

I guess you go with the Watch. But the public doesn't read forecast discussions. I guess people just check their weather apps nowadays. 

On the above: I'd rewrite 20% chance of less than 1" to 80% chance of greater than 1"  Then go from there... Ate least I know to expect snow.  

The probs we derive are generated from collaborated 3 hourly or sometimes 1 hour snowfall information blended with the National Center. These tend to miss the high end of storms, and I think tend to be conservative but the latter is my opinion only.  They are only as good as the modeling we chose to use... 

 

Note:  I add the 08z NDFD graphic for snowfall.  No wonder we are a little behind.  Nada Philly area and LI.  now the 17z... note big increases including 2"LI and 5" s NJ.  I think we had some info at 08z that ddid not get into the NWS NDFD forecast.  Hence the thread.

Screen Shot 2022-01-02 at 12.30.37 PM.png

Screen Shot 2022-01-02 at 12.30.16 PM.png

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23 minutes ago, wdrag said:

Added the criteria for 12 hour WATCH snowfall.  It's verified as an average in the zone-county. 

Color coded   here you are.

Also a link to the NWS snow probabilities and Winter Storm Severity Index is below, as of 10AM.

https://www.weather.gov/phi/winter

 

 

Screen Shot 2022-01-02 at 12.17.23 PM.png

Someone's gonna initially read this as an expected snowfall map.  Besides me, I mean :)

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